1-chloro-3,3,3-trifluoropropene (sometimes referred to as “1233”), which has a double bond in its structure and exhibits a very short lifetime in the air, is expected as being useful as an environment-adaptive hydrochlorofluorocarbon compound with no fear of ozone depletion and global warming. It is herein noted that, although 1-chloro-3,3,3-trifluoropropene can exist as trans and cis geometric isomers (sometimes referred to as “1233E” and “1233Z”, respectively), the term “1-chloro-3,3,3-trifluoropropene” used in the present specification refers to a trans isomer solely or a trans/cis mixture that contains a trans isomer as a main component and further contains an cis isomer.
It is feasible to produce 1-chloro-3,3,3-trifluoropropene by fluorinating 1,1,1,3,3-pentachloropropane (sometimes referred to as “240fa”) or 1,1,3,3-tetrachloro-2-propene (sometimes referred to as “1230za”) with hydrogen fluoride in the presence of a fluorination catalyst in a gas phase or a liquid phase.
For example, Patent Document 1 discloses a method for producing 1-chloro-3,3,3-trifluoropropene by reacting 1,1,1,3,3-pentachloropropane with hydrogen fluoride in a gas phase. In the production method of Patent Document 1, the purity of the 1-chloro-3,3,3-trifluoropropene is improved by bringing the reaction product into contact with water and thereby removing the hydrogen fluoride from the reaction product. Patent Document 2 discloses a method for producing 1-chloro-3,3,3-trifluoropropene by reacting 1,1,1,3,3-pentachloropropane with hydrogen fluoride at a temperature of 180° C. or higher without the use of a solvent. Further, the liquid-phase production of 1-chloro-3,3,3-trifluoropropene is generally conducted under pressurized conditions so that the resulting 1-chloro-3,3,3-trifluoropropene is obtained as a compatible mixture containing unreacted hydrogen fluoride and by-produced hydrogen chloride (hereinafter sometimes referred to as “HCl”) under pressure.
In the production process of a fluoroolefin, hydrogen fluoride is commonly used as a fluorination agent. As the fluoroolefin and the hydrogen fluoride are often compatible with each other, it is often the case that the product of the production process is in the form of a compatible mixture in which the fluoroolefin and the hydrogen fluoride are mutually dissolved.
In the case where the boiling point of the fluoroolefin is close to the boiling point (20° C.) of the hydrogen fluoride, the fluoroolefin and the hydrogen fluoride often form an azeotropic composition or azeotropic-like composition so that it becomes difficult to separate and purify the fluoroolefin and the hydrogen fluoride from the mixture thereof by distillation. It is herein noted that the term “azoptropic composition” refers to a mixture in which liquid and vapor phases in equilibrium are the same in composition; and the term “azeotropic-like composition” refers to a mixture in which liquid and vapor phases in equilibrium are similar in composition. These mixtures are difficult to separate by distillation.
It has been common practice to remove the hydrogen fluoride from the above-mentioned mixture by absorption of the hydrogen fluoride into water or an aqueous alkaline solution. In this technique, however, it is necessary to use a large amount of water for the removal of the hydrogen fluoride. It is also necessary to perform dehydration or drying operation for the removal of water content from the fluoroolefin. The dehydration or drying operation is complicated and requires equipment therefor. In general, the hydrogen fluoride can be removed by dilution with water and neutralization with an aqueous alkaline solution of sodium hydroxide, potassium hydroxide, calcium hydroxide, calcium carbonate etc. In industrial fields, the dilution of the hydrogen fluoride with the water and the neutralization of the hydrogen fluoride with the aqueous alkaline solution are often called “water washing” and “alkaline washing”, respectively.
Patent Document 3 discloses a method for separating, from a composition containing a fluoroolefin and hydrogen fluoride, the fluoroolefin by extracting the composition with an extractant.
Patent Document 4 discloses a method for producing 1-chloro-3,3,3-trifluoropropene, including the steps of: reacting 1,1,1,3,3-pentachloropropane at a temperature lower than 150° C. in the presence of a Lewis acid catalyst or a mixture thereof in a liquid phase within a reactor; continuously extracting the resulting hydrogen chloride and 1-chloro-3,3,3-trifluoropropene from the reactor; and isolating the 1-chloro-3,3,3-trifluoropropene from the extracted product. In Examples of Patent Document 4, the purity of the 1-chloro-3,3,3-trifluoropropene is improved by removing the hydrogen fluoride from the mixture of the 1-chloro-3,3,3-trifluoropropene and the hydrogen fluoride with the use of potassium hydroxide.
In the case of producing 1-chloro-3,3,3-trifluoropropene by reaction of 1,1,1,3,3-pentachloropropane with hydrogen fluoride, the resulting product is in the form of a solution mixture in which the 1-chloro-3,3,3-trifluoropropene, unreacted hydrogen fluoride and by-produced hydrogen chloride are mutually dissolved. In order to obtain the 1-chloro-3,3,3-trifluoropropene as simple substance, it is necessary to separate the 1-chloro-3,3,3-trifluoropropene from the hydrogen fluoride. However, the 1-chloro-3,3,3-trifluoropropene (boiling point: 19° C.) is azeotropic with the hydrogen fluoride (boiling point: 20° C.). Even when the separation of the 1-chloro-3,3,3-trifluoropropene and the hydrogen fluoride is attempted by distillation, it is very difficult to separate the 1-chloro-3,3,3-trifluoropropene and the hydrogen fluoride due to azeotrope formation between the 1-chloro-3,3,3-trifluoropropene and the hydrogen fluoride. Although it is conceivable to remove the hydrogen fluoride by absorption into the water or an aqueous alkaline solution, such removal operation requires much expense in time and effort and equipment as mentioned above.
For example, Patent Document 5 discloses a method for separating 1-chloro-3,3,3-trifluoropropene and hydrogen fluoride by distillation.
The separation method of Patent Document 5 is intended to separate the hydrogen fluoride from the azeotropic mixture of the 1-chloro-3,3,3-trifluoropropene and the hydrogen fluoride where it is rich in hydrogen fluoride, i.e., where the hydrogen fluoride is higher in content than the 1-chloro-3,3,3-trifluoropropene. In this separation method, the pure hydrogen fluoride is obtained as a distillation bottom product (distillation residue) whereas the azeotropic mixture of the remaining hydrogen fluoride and the 1-chloro-3,3,3-trifluoropropene is obtained as a distillate. As mentioned above, however, it is generally difficult to separate the hydrogen fluoride and the 1-chloro-3,3,3-trifluoropropene by distillation due to azeotrope formation between the 1-chloro-3,3,3-trifluoropropene and the hydrogen fluoride. Although it is conceivable to remove the hydrogen fluoride by absorption into water or an aqueous alkaline solution, such removal operation has to use a large amount of water and requires much expense in time and effort and equipment to dispose of the resulting hydrogen fluoride water and dehydrate and dry the 1-chloro-3,3,3-trifluoropropene. Under the above circumstances, there has been a demand to develop a method for separating 1-chloro-3,3,3-trifluoropropene and hydrogen fluoride by simple operation without complicated operation and equipment.
In this way, when 1,1,1,3,3-pentachloropropane or 1,1,3,3-tetrachloro-2-propene is fluorinated with excessive hydrogen for the industrial production of 1-chloro-3,3,3-trifluoropropene, the 1-chloro-3,3,3-trifluoropropene is obtained as a compatible mixture containing unreacted hydrogen fluoride and by-produced hydrogen chloride. It is not easy to separate such a compatible mixture of 1-chloro-3,3,3-trifluoropropene, hydrogen fluoride and hydrogen chloride by distillation due to azeotrope formation between the 1-chloro-3,3,3-trifluoropropene and the hydrogen fluoride. Further, it requires much expense in time and effort and equipment to remove the hydrogen fluoride by absorption into water or an aqueous alkaline solution.